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Here's why some 2017 model-year vehicles will have lower fuel economy figures

Changes to the coastdown part of the EPA's testing regimen will shift some window-sticker numbers, but not by much, thankfully.

EPA Window Sticker

Window stickers: It's all in your head.


It's all in our heads, you know. Numbers, math, all that stuff, it's just a figment of the human imagination, laid out over the order of the natural universe so that it makes some degree of sense to us. Despite model-year 2017 cars performing exactly the same as before, some will have lower fuel economy numbers on their window stickers, thanks to some adjustments in federal regulators' maths.

Last year, the US Environmental Protection Agency (EPA) outlined a list of changes for fuel-economy calculations in the 2017 model year. Now, we've reached a point where 2017s will start entering the market, and over at the EcoModder forum, they've found a few instances where fuel economy will drop. Vehicles like the Acura ILX, Kia Rio Eco and Toyota Camry will see small drops in either highway or both highway and combined figures.

The changes, as pointed out by Green Car Reports, relate to the "coastdown" portion of the EPA's tests. Coastdown requires an automaker to coast down (get it?) to a standstill from a set speed. The data gathered from that test is used in later procedures to produce the number that appears on the window sticker.

Coastdown is now measured more strictly, meaning some figures will appear lower, as Honda was quick to note during its press conference on the forthcoming 2017 Accord Hybrid. That's why the new Accord Hybrid will have lower fuel economy numbers than the outgoing model, despite actually performing better than before. Yeah, it's frustrating.

This change is due in part to the automakers themselves. The EPA lacks the time, money and manpower to do all these tests itself, so many are outsourced to the automakers, which then report to the EPA. Ford and Hyundai have been in trouble for fudging data in the past, and Mitsubishi is currently in hot water for manipulating its coastdown data, as well. Thus, Dad's not going to let the kids stay home alone without a few more safeguards in place.

This'll have the biggest effect on number-conscious buyers and PR companies with automotive accounts, the latter having to deal with explaining why a car can get lower fuel economy without changing anything. But remember -- nothing's really changed. Your right foot is still the biggest variable in real-world fuel economy, and the feds can't adjust that. It's easy enough to exceed EPA fuel-economy estimates in most new cars, so long as you're not driving like a total pillock.

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